cab and the Smart Factory:
Networked labeling with OPC UA

Event-driven labeling

Asking a label printer at the press of a button how he is doing is outfashioned. Today, smart devices automatically indicate that they want to be maintained or that the material to be printed resp. the ribbon are running short and must be replaced. Labels can be loaded remotely, as well as label characteristics can be read and variable data can be exchanged for printing. Operating parameters such as the print head's running performance so far, its temperature or the number of labels still to be printed in the current job are displayed just in time. Information is transferred by the printer to the plant control system, which identifies and interpretes the information and directly initiates the appropriate measure.

OPC UA as a superior control system offers the advantage of bringing together production data, alarms, events and data history controlled by software under one roof. It integrates and unifies various address spaces and the interfaces to be accessed.

---

---

OPC UA with cab printers

OPC UA features that are at present supported by cab devices* are as followed:

•  Communication Stack
       OPC UA binary protocol
• Encryption
       none
       Basic128Rsa15
       Basic256Sha256
• Authentication
       anonymous
       user name/password

While fully authenticated users may have full access to the provided data model, anonymous users may only access printer nodes read-only and are not granted to call any method, even if the method does not change the printer's configuration or state.

• OPC UA Services
       SecureChannel Service Set
       Session Service Set
       Attribute Service Set: reading/writing of attributes, events, no historical data access
       Method Service Set
       MonitoredItem Service Set
       Subscription Service Set
       View Service Set

The OPC UA Server can be activated under Settings / Interfaces / Network Services.

* cab label printers SQUIX, MACH 4S, EOS2, EOS5, HERMES Q, PX Q, labeling heads IXOR

Information model

cab printers implement the OPC UA Device Integration (DI) model. Two namespaces are provided:

http://cab.de/printer for print job monitoring and control
http://cab.de/printer/setup for device configuration

The functions displayed on the following pages correspond to the current status and are continuously further developed.

Namespace http://cab.de/Printer

This namespace provides access to the current state of the printer, including the state of the I/Os, printer model information or any information about the current job status.

Node name	Node class	Description
Printer	Object	The primary entry point for accessing the printer's information model
FPGARevision, Manufacturer, Model, SerialNumber, SoftwareRevision, HardwareRevision	Variable	Supply hardware and software versioning information
Bitmap	Method	Returns the last printed label in .png format
Screen	Method	Returns a screenshot of the printer's display in .png format
I/O	Object	Provides software access to the printer's I/O; generates IOStatusChangeEvent
LBLWARN	Variable	Warning before end of labels
RIBERR	Variable	Transfer ribbon to end
RIBWARN	Variable	Warning before end transfer ribbon
SetInput	Method	Set input of I/O interface: PAUSE, LBLROT
LabelBitmap	Method	Print image of the current label in .png format. Unlike the bitmap method, label orientation and size are taken into account here
ENDPOS	Variable	Applicator is in labeling position
ERROR	Variable	The printer is in error state
FEEDON	Variable	A feed is currently in progress, i.e. paper is moving
HOMEPOS	Variable	Applicator is in home position
JOBRDY	Variable	Print data is available
MEDERR	Variable	End of paper or ribbon
PEELPOS	Variable	Label is in peel position
READY	Variable	Printer is ready
I/O Status	Variable	Output status of the I/O interface, defined by a combination of the following values: RIBWARN 1  HOMEPOS  8  ERROR    64  RIBERR  512 ENDPOS  2  PEELPOS 16  READY   128  MEDERR 1024 FEEDON  4  JOBRDY  32  LBLWARN 256  (partly only HERMES Q)
TriggerInput	Method	Allowing to trigger an I/O input, one of FSTLBL, REPRINT, START, LBLREM, JOBDEL, RSTERR, STOP, LBLFEED
Interpreter	Object	Job status information; generates ErrorEvent, JobInfoEvent and JobFinishEvent
JPhase	Variable	Current state of the JScript interpreter
QueryObject	Methode	Query of existing JScript objects
Current Label	Object	Available whenever a job is executed by the Interpreter
Current Id	Variable	Unique job Id of current job
Current Name	Variable	Job name; name of the current job in Interpreter as provided by JScript j command
Current Content Fields	Object	Root node of named label content fields. They may be replaced by setting the value of the content nodes.
abc Status	Variable	Current status of integrated abc basic interpreter: one of Idle, Compiling, Running, RuntimeError oder SyntaxError
Active	Variable	Indicates printer is active, i.e. interpreting or printing
Available Space	Variable	Available print queue memory in %
ESCs	Variable	String containing the result of JScript's ESCs command
ESCz	Variable	String containing the result of JScript's ESCz command
Error	Variable	Provides detailed error information as in the ESCs command; the numeric value may be interpreted as an ASCII char, e.g. 45 == '-' No error
Labels To Print	Variable	Labels to be printed within the current job
Last Job	Variable	Name of last job; see the corresponding direct JScript command j
Online	Variable	Printer is ONLINE, i.e. the graphical user interface shows the home screen
Paused	Variable	Printer is in PAUSE
CancelJob	Method	Allows the cancellation of the current print job
LoadLabel	Method	Allows to load a label from any printer storage
PrintData	Method	Allows to send JScript print data directly to the printer
TotalCancel	Method	Cancels all print jobs scheduled or currently printed by the printer
Ribbon	Object
Ribbon RibbonDiameter	Variable	Detected ribbon diameter in millimeters
Ribbon RibbonLow	Variable	Indicates whether the ribbon is considered to be low in reference to the corresponding printer setting
Statistics	Object
Statistics Labels	Variable	Number of labels printed
Statistics Operating Time	Variable	Uptime of printer in minutes
Statistics Thermal Direct	Variable	Printed thermal direct material in millimeters
Statistics Thermal Transfer	Variable	Printed thermal transfer material in millimeters
Paper
Paper Diameter	Variable	Calculated diameter of the label remnant at the unwinder in millimeters (HERMES Q only)
Paper Low	Variable	Low label residual quantity according to setting in printer menu (HERMES Q only)
SubDevices	Object
Applicator*	Object
Barcode Verifier*	Object
Cutter*	Object
Cutter* Can Perforate	Variable	The attached cutter device may be used for perforation.
Cutter* Has Stacking Box	Variable	The attached cutter device has a stacking box.
Demand Sensor*	Object
Sensor Status	Variable	Photo sensor status
Rewinder*	Object
Ribbon Saver*	Object	Detected ribbon diameter in millimeters
Ribbon Sync	Variable	Ribbon Saver is initialized and fully operational.
Ribbon Head State	Variable	Current state of the print head, one of Printing or Saving
Ribbon Synchronize	Method	Issues a ribbon saver synchronization command; only relevant for service tasks
Ribbon ToggleHead	Method	Toggles the head state up or down; only relevant for service tasks
TPH 1	Object	Print head information
TPH 1 Model	Variable	Human readable description string of the installed print head
TPH 1 SoftwareRevision	Variable
TPH 1 Open	Variable	Open state
TPH 1 SerialNumber	Variable	Serial string of print head
TPH 1 Temperature	Variable	Current print head temperature in °C
TPH 1 Statistics	Object	Statistics correlated with the print head
Storage	Object
FileDelete	Method	Deletes a file on a disk of the printer
FileDownload	Method	Downloads a file on a disk of the printer to the client
FileList	Method	Lists all files on a disk of the printer
FileUpload	Method	Downloads a file of the client to a disk of the printer
FontList	Method	Queries the fonts available on the printer
IFFS	Object	(I)nternal (F)lash (F)ile (S)ystem
IFFS IFFS Available Space	Variable	Space available on the file system in kB
IFFS Capacity	Variable	Capacity of the file system in kB
SD Card	Object
SD Card SD Card Attached	Variable	Indicates whether the file system is attached or not
USB Memory	Object

* Optional node, only available with service key attached

Important note: According to the OPC UA Device Integration specification, methods must always be called in the MethodSet of the device, even if they are linked in separate FunctionalGroup for better assignment. A call via the FunctionalGroup always leads to an error.

Namespace http://cab.de/Printer/Setup

This namespace provides full access to the printer's configuration tree, which is modeled in the same way as the setting levels of the graphical user interface. The actual position of configuration parameters within the tree is subject to change, so it is not safe to look up a node via it's browse path. Instead, configuration nodes may be directly accessed by their unique string identifier.

Node name	Node class	Description
Setup	Object	This sub-node of the Printer node is the primary entry point for accessing the printer's setup; generates SetupValueChangeEvent and SetupVisibilityChangeEvent aus
SetOpcUaClientUrl	Method	Storage of an OPC UA server address for use in standalone mode.
ExportSettings	Method	Exports printer configuration in .xml format
ImportSettings	Method	Imports printer configuration in .xml format
ImportCertificateTLS	Method	Imports a custom TLS certificate
Reset	Method	Reset to factory defaults
ResetPasswords	Method	Reset passwords to factory defaults
<SetupFolder>	Object	Contains setup values
<SetupValue>	Object	A setup value which can be edited
IsActive	Variable	This setup parameter is currently accessible in the printer's graphical user interface.

The following setup value types are available:

• Boolean values
• Enumerations
• String values contain the fields
  MinLen
  MaxLen
  Regex, an optional regular expression which will be applied to a write operation on the attribute's value
• Numeric values contain the fields
  Range
  Step
  ToggleInt (optional, for display purpose)
  Unit (optional, for display purpose)
• Passwords contain minimum and maximum length attributes just like string values

Important note: According to the OPC UA Device Integration specification, methods must always be called in the MethodSet of the device, even if they are linked in separate FunctionalGroup for better assignment. A call via the FunctionalGroup always leads to an error.

Events

Beyond OPC UA standard events, cab printers provide the following supplementary events.

Event name	Type	Description
ErrorEvent		Emitted whenever a printer error occurs; generated by node Interpreter
Message	LocalizedText	Error message
Detail1	LocalizedText	More details about the supplied error
Detail2	LocalizedText	Even more details about the supplied error
JobInfoEvent		Emitted whenever a label is printed; generated by node Interpreter
LabelNo	Int32	Number of label within current job
JobSize	Int32	Size of job
IsTestPrint	Boolean	Indices that currently printed label is a test print
JobFinishEvent		Emitted whenever a job is finished and the printer returns to Idle; generated by node Interpreter
no further fields
SetupValueChangeEvent		Emitted whenever a setup value changes; generated by node Setup
SourceName	String	The name of the affected setup parameter
SetupVisibilityChangeEvent		Emitted whenever a setup value changes its visibility state, typically due to interdependencies; generated by node Setup
SourceName	String	The name of the affected setup parameter
IOStatusChangeEvent		Emitted whenever the I/O status of the device changes; generated by node I/O
Status	UInt32	New printer status as described in Printer->IO->Status

Limitations: The OPC UA stack implementation currently does not support:

• Different kinds of Monitored items - either Change notify or Event notify - within a single subscription though multiple Monitored items of the same kind in a subscription is allowed
• Where clauses in Monitored items requests
• Alarms and conditions

OPC UA Client Support in the printer

Using the JScript special command OPCUA the printer can read data from OPC UA servers in standalone mode and insert it into the label layout:

   m m
   J
   H 75,0
   S l1;0,0,25,29,50
   E OPCUA;opc.tcp://192.168.200.71:4840
   T 20,20,0,3,10;[OPCUA:2:DeviceSet,3:Printer,2:SoftwareRevision]
   A 1

In order to be able to address several OPC UA servers, the concept of a slot is used. A slot number can be added to the token OPCUA, so that up to five different server systems can be queried:

   m m
   J
   H 75,0
   S l1;0,0,25,29,50

   ; Connection using a user name and password
   E OPCUA-0;opc.tcp://opcuser:opcpass@192.168.200.71:4840

   ; Anonymous connection
   E OPCUA-1;opc.tcp://192.168.200.53:4840

   T 10,10,0,3,10;SW Rev Drucker 1: [OPCUA-0:2:DeviceSet,3:Printer,2:SoftwareRevision]
   T 20,20,0,3,10;SW Rev Drucker 2: [OPCUA-1:2:DeviceSet,3:Printer,2:SoftwareRevision]
   A 1

As an alternative to specifying the browsepath, node IDs can also be specified for the data query in the OPCUA special command:

   m m
   J
   H 75,0
   S l1;0,0,25,29,50
   E OPCUA;opc.tcp://192.168.200.71:4840
   T 20,20,0,3,10;[OPCUA:ns=3;i=50723]
   T 10,10,0,3,10;[OPCUA:ns=4;s=ID_BACKFEED]
   A 1

The following data types are supported:

•      integer numeric data types
•      floating point values
•      String, ByteString, XmlElement
•      Boolean values
•      LocalizedText
•      DateTime
•      Range
•      EUInformation
•      Enumerations

The connection information does not necessarily have to be stored in the label but can be stored in the global configuration of the printer instead. The OPC UA function SetOpcUaClientUrl is used for this purpose. By specifying the desired slot and the address to be used, up to 5 different connection information can also be stored here. In this case the E command in the label can be omitted.

For developers

Our GitHub repository provides detailed technical information and sample code for our OPC UA server. Implementations are available in C++ (using the open62541 library) and Python (using the python-opcua library).

 

---

 

January 2021